1. Field of the Invention
The present invention relates to a microorganism capable of producing organic acids and a process for producing organic acids using the microorganism, and more particularly, to a new microorganism, Mannheimia sp. 55E, capable of producing organic acids and a process for producing organic acids through incubation of the microorganism in anaerobic or aerobic conditions.
2. Description of the Related Art
Thanks to the progress of the petrochemical industry, most chemical substances have been produced from petroleum and natural gases. However, restrictions on the production of chemical substances is becoming more rigid worldwide with the recent rise of environmental concerns such as global warming, thereby increasing the need for the development of an alternate to the conventional process of producing chemicals.
The rapid advance of microorganism cultivation and genetic engineering technology has placed biochemical productions of chemical substances at a competitive position to the conventional petrochemical process. Biochemical methods are known to be environmentally compatible, thus being capable of solving environmental problems, because they can suppress generation of gases that cause global warming, such as carbon dioxide (CO2), with use of inexpensive renewable resources. Therefore, approaches to cost reduction through isolation of new strains and process improvement are getting spread in the biochemical field. In addition, increased market values of biochemical materials have boosted research into the production of the biochemical materials from biomass using microorganisms throughout the world.
In particular, focus on biochemical materials, particularly succinic acid and lactic acid, is increasing due to their cost competitiveness and wide applications as biodegradable plastic monomers, food additives, and intermediate products of other organic compounds.
A study on the biological production of succinic acid was started in 1938 by Lockwood who reported production of succinic acid from sugar using Fusarium martii with a 18% yield. It was reported that production of succinic acid through glycolysis of a variety of anaerobic microorganisms such as Succinivibrio dextrinosolvens, Fibrobacter succinogenes, and Ruminococcus flavefaciens (Zeikus, Annu, Rev. Microbiol., 34:423–464, 1980). Any microorganism capable of producing succinic acid with high yield for industrial use, except for Anaerobiospirillum succiniciproducens known to be able to produce succinic acid from glucose with high yield and concentration in the presence of excess carbon, was not disclosed (David et al., Int. J. Syst. Bacteriol., 26:498–504, 1976). Because Anerobiospirillum succiniciproducens is an obligate anaerobic microorganism, stable fermentation using the microorganism for production of the succinic acid is not ensured even with the presence of trace oxygen.
A variety of factors, such as production yield, fermentation conditions, etc., should be carefully considered for economical production of organic acids through microorganism fermentation. In particular, isolation of new microorganisms capable of producing organic acids has priority over the other factors to consider. Most microorganisms currently available to produce organic acids are anaerobic microorganisms, so costly cultivation equipment is required, and it is very likely that intended fermentation fails due to the presence of trace oxygen. Therefore, there is an urgent need for development of microorganisms having a tolerance to oxygen and capable of producing organic acids with high yield.
As a result of research on such oxygen-tolerant microorganisms being able to produce organic acids with high throughput, the present inventors have succeeded in separating a new facultative anaerobe, Mannheimia sp. 55E, from the bovine rumen fluid, and identifying the new microorganism to be tolerant of oxygen and able to produce organic acids in anaerobic and aerobic conditions.